Held captive: Scott and Jean Adam, owners of the the Quest, were shot dead by pirates who hijacked their boat on Friday. The U.S. Navy had been in negotiations with their captors

The U.S. military today reacted with fury after the pirates who killed four Americans claimed the Navy shot at them first.Jean and Scott Adam, from California, were killed alongside Phyllis Macay and Bob Riggle from Seattle, Washington, in the early hours of yesterday. U.S. Navy officials had been negotiating with the pirates when, without warning, the bandits fired a rocket-propelled grenade at their warship.

Held captive: Scott and Jean Adam, owners of the the Quest, were shot dead by pirates who hijacked their boat on Friday. The U.S. Navy had been in negotiations with their captors

The grenade missed the USS Sterett, which was 600 yards from the hijacked yacht, the Quest.

Immediately afterwards, at around at around 9am local time (3am ET) gunfire erupted inside the cabin of the Quest, the Navy said.

Several pirates then moved onto deck with the hands in the air - as if to surrender - as a rescue force of 15 Navy Seals rushed onboard. The pirates began shooting at the Seals, and in the ensuing battle, two of the bandits were killed.

All four hostages had already been shot.

Today, however, pirate sources in touch with news agencies disputed the Navy's version of events.

Two Somali pirates spoke with Reuters by telephone, claiming the murders had been their response to a U.S. attack.

'Our colleagues called us ... (saying) that they were being attacked by a U.S. warship,' said a pirate who identified himself as Muhammad.

'The U.S. warship shot in the head two of my comrades who were on the deck of the yacht by the time they alerted us,' he said. 'This is the time we ordered the other comrades inside the yacht to react - kill the four Americans because there was no other alternative - then our line got cut.'

But Lieutenant-Commander Bill Speaks, a spokesman for U.S. Central Command, said: 'This is absolute nonsense. It is false.'

Hostages: Phyllis Macay and Bob Riggle, both from Seattle, were aboard the Quest with the Adams when it was hijacked. They were also killed

The Navy Seals captured and detained 13 pirates.

The remains of two other pirates who had been dead for some time were also found. They appeared to have been killed by their fellow pirates, the military said.